Skin is the largest protective barrier for the human body, and is able to prevent water loss, entering of pathogens, and damages by various harmful environments. Heavy exposure to ultraviolet (UV), ionizing radiation, drugs, or xenobiotics induces generation of reactive oxygen species (ROS) and free radicals in skin. When accumulating ROS and free radicals exceed the antioxidant capacity of cells or tissues, oxidative stress occurs. Particularly, ROS and free radicals react with cell components (including DNA, proteins, and lipids), such that skin is adversely influenced. It has been reported that ROS and free radicals not only play an important role in melanogenesis, but also lead to delay of wound healing (Kim Y. J. and Yokozawa T. (2009), Biol. Pharm. Bull., 32:1155-1159; and Kurahashi T. and Fujii J. (2009), J. Dev. Biol., 3:57-700).
Melanogenesis is a process where tyrosine in melanocytes is converted to melanin under catalysis of tyrosinase and a series of oxidation-reduction reactions. Melanogenesis is normally induced by UV radiation (particularly UV-B). When skin is exposed to UV radiation, the ROS and free radicals generated in keratinocytes induce expression of tumor protein 53 (p53), thereby giving rise to expression of the proopiomelanocortin gene (POMC gene) and releasing POMC-derived peptides such as α-melanocyte stimulating hormone (α-MSH) and adrenocorticotropic hormone (ACTH). Further, the tyrosine gene in melanocytes is expressed, such that a large amount of melanin accumulates on skin.
When skin damage (for example, scald, trauma, surgical injury, contusion, etc.) leads to wound, an inflammatory response is triggered at the wound site. A tremendous amount of ROS and free radicals are released to assist immune cells in fighting against pathogens. However, excess ROS and free radicals cause damage to the tissues surrounding wound. In the wound healing process, fibroblasts aggregate at the wound site to proliferate and to release growth factors, thereby resulting in angiogenesis, epithelialization, collagen remolding, and so forth. Excess ROS and free radicals not only inhibit angiogenesis, but also inactivate the enzymes involved in signal transduction pathways, such that wound healing is hindered.
In recent years, the demand for skin whitening, moisturizing, facilitation of wound healing, and antioxidation have been increasing. Particularly, use of natural ingredients, which do not cause undesired harmful side effects on skin, has become a trend for the field of aesthetic medicine. Therefore, to satisfy such great demand, researchers in the health care industry and cosmetic industry endeavor to look for safe active ingredients, which are effective in whitening, moisturizing, wound healing, and antioxidation, from traditional Chinese medicines (TCM) or plants.
Syzygium samarangense (common name: wax apple; Pinyin: lian wu) is a perennial evergreen tree which belongs to the family Myrtaceae and the genus Syzygium, and which has opposite simple leaves that are elliptical in shape, axillary flowers that have pale yellow corolla, and berries that are obconical in shape. Syzygium samarangense is distributed over Taiwan, Indonesia, Philippines, Malaysia, and so forth. The common cultivars of Syzygium samarangense fruits include dark red cultivars, pale red cultivars, “Black Pearl”, “Black King Kong”, “Black Diamond”, etc. Syzygium samarangense fruits are frequently used. In the field of Chinese fold medicine, Syzygium samarangense fruits are used for lung nourishing, cough suppression, sputum reduction, blood cooling, and induction of astringency. In addition, Syzygium samarangense fruits are considered to be effective in relieving fever, promoting dieresis, and reducing mental strain.
The application of the Syzygium samarangense extract in the pharmaceutical field has been studied. For instance, as reported in the thesis written by Pei-Wen Lo from the Department of Nutrition and Food Science at Fu-Jen Catholic University (“Evaluation of the Antioxidative and Free Radical-scavenging Activity of Several Taiwan Unique Fruits”), the antioxidation efficacy regarding the Syzygium samarangense fruit and other types of fruits was investigated. Specifically, 14 types of fruits (fruits of Citrus sinensis Osbeck, Citrus tankan Hayata, Citrus grandis (L) Osbeck, Citrus grandis Osbeck, Citrus micro carpa, Fragaria ananassa Duch, Hylocereus undatus, Syzygium samarangense, Diospyros kaki L., Mangifera indica L., Carica papaya L., Zityphus jujuba, Averrhoa carambola L., and Psidium guajava L.) were subjected to lyophilization and grinding to form powder. 10 g of powder of a respective fruit was subjected to a 6-hour extraction treatment using 100 mL of methanol, followed by a filtration treatment with a filter paper. The resulting filtrate was subjected to concentration and drying. Thus, 14 methanol extracts of fruit were obtained, and were tested for the antioxidation efficacy. The experimental results indicate that the aforesaid 14 methanol extracts of fruit exhibit different levels of activities in different tests. Particularly, via the test for the α,α-diphenyl-β-picryhydrazyl (DPPH) radical scavenging ability, it was found that the methanol extract of a fruit material (containing a peel and a pulp) of Syzygium samarangense has the worst DPPH radical scavenging ability. Furthermore, the result of the test for the ability to inhibit superoxide anion generation reveals that the methanol extract of the fruit material of Syzygium samarangense is not able to inhibit superoxide anion generation, but instead induces superoxide anion generation.
In addition, as described in the thesis written by Yi-Zhen C en from the Institute of Cosmetic Science at Chia Nan University of Pharmacy & Science (“Application of Extracts from Wax Apple Flowers on Antioxidantion”) the antioxidation efficacy and tyrosinase inhibition ability regarding the Syzygium samarangense flower were examined. Specifically, 50 g of dry powder of a Syzygium samarangense flower was subjected to a one-hour extraction treatment with 500 mL of 80% methanol, and 50 g of dry powder of a Syzygium samarangense flower was subjected to a one-hour extraction treatment with 500 mL of water. Subsequently, a filtration treatment was conducted using a filtration paper. The resulting two filtrates were subjected to concentration and lyophilization, such that a methanol extract of Syzygium samarangense flower and a water extract of Syzygium samarangense flower were obtained. The aforesaid two extracts were tested for the antioxidation efficacy and tyrosinase inhibition activity. In most of the tests for the antioxidation efficacy (i.e. the tests for the superoxide anion scavenging ability, lipid peroxidation inhibition activity, and ferrous ion chelating ability), it was found that the antioxidation efficacy of the aforesaid water extract is better than that of the aforesaid methanol extract. However, the results show that the tyrosinase inhibition ability of the aforesaid methanol extract is significantly better than that of the water extract.
TW 1465258 discloses an ethanol extract of Syzygium samarangense flower (which has skin whitening and anti-aging effects) and a preparation process thereof. The aforesaid preparation process includes subjecting dry powder of Syzygium samarangense flower to an extraction treatment with 95% ethanol, subsequently conducting a filtration treatment, and subjecting the filtrate thus obtained to a concentration treatment. It was verfied from experiments that the aforesaid ethanol extract of Syzygium samarangense flower is effective in serving as an antioxidant, inhibiting tyrosinase, and facilitating collagen formation.
In spite of the aforesaid documents, the researchers in this field still endeavor look fora more satisfactory bioactive component from Syzygium samarangense. In a previous study, the applicants found that a water extract of a fruit material of Syzygium samarangense is slightly effective in inhibiting the activity of tyrosinase, enhancing the moisture-retaining capacity of skin, and improving would healing (such finding has never been published). In a further study, the applicants surprisingly observed that a hydrolysate, which is prepared by subjecting a water extract (obtained from a fruit material of Syzygium samarangense) to a hydrolysis treatment with bromelain, can more effectively inhibit the activity of tyrosinase, enhance the moisture-retaining capacity of skin, and improve wound healing compared to the water extract from which it is prepared. Thus, it is expected that a hydrolysate of water extract of Syzygium samarangense can serve as an active ingredient for a cosmetic or pharmaceutical composition.